DESCRIPTION: (Principal Investigator's Abstract) The development of new processes by which the efficiency of pharmaceutical synthesis can be improved is a central goal of biomedical research. The elucidation of novel reaction types that enable selective organic transformations remains fundamental to this endeavor. The research proposed within this grant application is concerned with the discovery and application of versatile new methods for molecular annulation. During the preceding funding period, the Principal Investigator and his coworkers have shown that a variety of stereochemically diverse heterocycles can be prepared with excellent selectivity by an experimentally straightforward class of chemical reactions. It is expected that the use of this new reaction type, as well as mechanistically related variants of it, will permit rapid access to important classes of synthetic intermediates for pharmacological research. This proposal outlines our immediate plans for the pursuit of this objective and details specific applications to the synthesis of selected bioactive molecules.